(As far as I know, all of the Galaxy Tab 8.9 and Galaxy Tab 7 Plus devices are sold unlocked, for now.)
Do you have any specific links?
I don't have a 10.1, but I did spend a few hours reading through many of those threads last week before I decided against purchasing one for my wife. (We ended up going with the 7+ model instead.)
For what it's worth, my understanding is that there are workarounds to flash an unsigned kernel, it's just a real pain. Also, I think you would get the message you are seeing even if it were unlocked... my Galaxy S2 gives me the same warning before letting me into download mode.
Also, I think you would get the message you are seeing even if it were unlocked
Right. I was thinking that if it were locked it wouldn't have such a thoughtful warning and the option to proceed. But this reasoning could be wrong obviously.